I created a slide in and slip on Arduino Uno/Mega mount for a breadboard. The breadboard style that has the thin metal base with terminal screws as power posts. (refer to pics)
You simply slide the Uno or Mega in the channels (it's snug) and slide the bottom on the breadboard base. The gap to slide it on the metal is about 2mm, so it can be used for other things as well. The bracket is on a 45 degree angle.
I wanted something that allowed me to see the Arduino with the breadboard and this has a good look to it.